From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7D2CC433DB for ; Sat, 9 Jan 2021 21:05:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8387823888 for ; Sat, 9 Jan 2021 21:05:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726062AbhAIVFd (ORCPT ); Sat, 9 Jan 2021 16:05:33 -0500 Received: from netrider.rowland.org ([192.131.102.5]:49201 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726005AbhAIVFd (ORCPT ); Sat, 9 Jan 2021 16:05:33 -0500 Received: (qmail 1136841 invoked by uid 1000); 9 Jan 2021 16:04:52 -0500 Date: Sat, 9 Jan 2021 16:04:52 -0500 From: Alan Stern To: Eugene Korenevsky Cc: linux-usb@vger.kernel.org, Greg Kroah-Hartman Subject: Re: [PATCH v3] ehci: fix EHCI host controller initialization sequence Message-ID: <20210109210452.GA1136657@rowland.harvard.edu> References: <20210109181828.GA7585@himera.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210109181828.GA7585@himera.home> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Sat, Jan 09, 2021 at 09:18:28PM +0300, Eugene Korenevsky wrote: > According to EHCI spec, EHCI HC clears USBSTS.HCHalted whenever USBCMD.RS=1. > However, it is a good practice to wait some time after setting USBCMD.RS > (approximately 100ms) until USBSTS.HCHalted become zero. > > Instead, previous version of ehci_run() wrote 1 to USBCMD.RS, issued read to > USBCMD and waited for 5 ms. > That worked incorrectly at least for VirtualBox's EHCI virtual HC and caused > accidental hangs. > > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=211095 > Reviewed-by: Alan Stern > Reviewed-by: Greg Kroah-Hartman This is a big no-no! You must not add other people's Reviewed-by or Acked-by tags to a patch unless they give you explicit permission to do so. > Signed-off-by: Eugene Korenevsky > --- > drivers/usb/host/ehci-hcd.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c > index e358ae17d51e..f3b73b5ab6e3 100644 > --- a/drivers/usb/host/ehci-hcd.c > +++ b/drivers/usb/host/ehci-hcd.c > @@ -574,6 +574,7 @@ static int ehci_run (struct usb_hcd *hcd) > struct ehci_hcd *ehci = hcd_to_ehci (hcd); > u32 temp; > u32 hcc_params; > + int rc; > > hcd->uses_new_polling = 1; > > @@ -629,9 +630,19 @@ static int ehci_run (struct usb_hcd *hcd) > down_write(&ehci_cf_port_reset_rwsem); > ehci->rh_state = EHCI_RH_RUNNING; > ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag); > - ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */ > + > + /* Wait until HC become operational */ > msleep(5); > + rc = ehci_handshake(ehci, &ehci->regs->status, STS_HALT, 0, 100 * 1000); You should not remove the ehci_readl call above. With that line gone, the PCI bus might not send the new value of configured_flag to the controller until after the 5-ms sleep has ended, which makes the msleep useless. Alan Stern > + > up_write(&ehci_cf_port_reset_rwsem); > + > + if (rc) { > + ehci_err(ehci, "USB %x.%x, controller refused to start: %d\n", > + ((ehci->sbrn & 0xf0)>>4), (ehci->sbrn & 0x0f), rc); > + return rc; > + } > + > ehci->last_periodic_enable = ktime_get_real(); > > temp = HC_VERSION(ehci, ehci_readl(ehci, &ehci->caps->hc_capbase)); > -- > 2.20.1 >